Gasoline fuel may be sold a variety of different octane levels. Higher octane fuels tend to be more knock resistant than lower octane fuels. Knock is a pinging sound produced by an engine and caused by a rapid pressure rise in a cylinder that results from ignition of end gases in the cylinder by way of increased temperatures and pressures in the cylinder due to a flame front produced via spark ignition progressing across the cylinder. Knock may cause engine degradation and is often discouraged at higher intensity levels. Knock may more often occur at higher engine speeds and torques since cylinder wall temperatures and cylinder air-fuel mixture temperatures may increase at higher engine speeds and torques. Engine compression ratio may also affect an engine's propensity for knock. For example, an engine having a higher compression ratio may be more prone to knock than an engine having a lower compression ratio. Higher octane fuel may be recommended by a vehicle manufacturer to reduce the possibility of knock in some vehicles, but the higher octane fuel may increase vehicle operating expense since higher octane fuel is often more expensive than lower octane fuel. Nevertheless, if the vehicle is not operated at higher engine speeds and torques, the increased cost of higher octane fuel may be unwarranted because the vehicle may not knock at lower speeds and torques.
The inventors herein have recognized the above-mentioned issue and have developed a vehicle method, comprising: retrieving engine operating information from sensors; at a substantially same time, estimating cost per unit distance traveled via a vehicle for a higher octane fuel and a lower octane fuel based on the engine operating information; and displaying cost per unit distance traveled by the vehicle for the higher octane fuel and the lower octane fuel at a same time.
By retrieving past or future vehicle information and estimating a cost per unit distance traveled by a vehicle for lower and higher octane fuels, it may be possible to provide the technical result of reducing vehicle operating cost while at the same time reducing a possibility of engine knock. For example, engine speed values, torque values, and time spent at the speeds and torques over a driving route may be stored to memory or estimated based on road speed limit. The engine torque values and speed values index brake specific fuel consumption (BFSC) functions or tables for higher and lower octane fuels that output fuel consumed per unit time (e.g., gallons/hour or liters/hour) at the particular speed and torque values. The table outputs are multiplied by the time the engine operates at the particular engine speed and torque to determine the amounts of fuel consumed if the engine were operated with higher octane fuel and lower octane fuel. The amounts of higher and lower octane fuel estimated consumed is multiplied by the cost per unit volume of fuel (e.g., $4.00/gallon) to provide the estimated cost of fuel consumed to travel the route. The estimated cost of higher and lower octane fuel consumed to travel the route is divided by the distance of the travel route to determine fuel costs per unit travel distance for lower and higher octane fuels. The estimated fuel cost to operate the vehicle over the travel route for the higher and lower octane fuel may be displayed to a driver or used as a basis for a vehicle controller to select a fuel from a fuel pump. In this way, a driver or vehicle controller may be presented with information to make an informed fuel octane selection.
The present description may provide several advantages. For example, the approach may reduce a vehicle's operating cost. Additionally, the approach may provide an indication to a driver that engine knock may be encountered over a driving route if lower octane fuel is supplied to the vehicle. Further, the approach may take present weather and future weather into consideration when determining cost to operate the vehicle with higher and lower octane fuels.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.